Norcim rc electronics page 16……
Hello! The following notes are taken from reader input to the Norcim website (obtained from emails). No apologies are made for the complete randomness of content. These notes are intended to cover a wide field of Radio control modelling including model history, R/C electronic Snippets, model engines stuff, in fact anything connected with radio control models.
PETER ALLEN kicks this page off with a couple of photos he sent with memories of being part of the ‘soldering set’ (as Steve Jobs called us!). The first photo shows one of his micron kit receivers. There is little data available on this version. Peter comments… I'm in Tasmania, Australia. Must have bought a system kit in abut 1974. Purchased servo kits and parts over time then parts for a system 80 FM Tx and several FM Rx's over time. The mini 2 deck Rx was very successful - I also built a few for other people for 1/2Aand 1/4 Midget pylon racing - a severe environment - never had a problem with any of them.
Somewhere in there I built a Royal Omega Tx - awful amount of money and 27 pages of instructions. My user units these days are Futaba (all bought second hand, I prefer them pre scratched) 8UAP, 9CAP,9Z. All module Tx's, so use 2.4G system or 36M FM. Now you can buy a 9 gm servo for under A$2 !!!!
After some enquiries, it seems that assembly drawings and any schematics have been lost with history. Looking at Peter’s excellent original picture (this one is fiddled with to suit the web page) it would seem that the design looks very much like a Mike Dorfler circuit that was printed in ‘American Modeller’ magazine around that period. (1974). The line up looks like a 27MHz amplitude modulated receiver with a double coil front end. It looks likely that a JFET transistor was used as a mixer ( Mike Dorfler pioneer style). This looks followed by the typical three stage 455KHz IF can amplifier, typical of most radios of the time. The decoder IC was almost certainly a MC4015 design. The MC4017 decoder used extensively by Micron came later.
OK….we have now found some info on this receiver and a sample sent to us by Peter A has been looked at by David Caudrey. David has produced the original circuit and this is shown next along with some historic assembly details that we have been able to gather. The second picture shows Peter’s flying buddies. Probably taken at the flying site just before they all let those ‘Things’ loose into the big blue yonder. One thing puzzles me though! If you get that lot into the air…..how do you know which one is yours!! AH well, I suppose they are all different colours. OH by the way, Peter is the hansom one of the bunch, back left. ‘Good On Yer Pete’ ! (excuse my accent)
DAVIDS REVERSE ENGINEERED CIRCUIT OF THE MICRON 27/35MHZ RADIO CONTROL RECEIVER. ∆
THE LAYOUT OF THE 27/35MHZ AM RECEIVER ON THE PRINTED CIRCUIT BOARD. Later addition was the 2.2 Meg Resistor which prevented the automatic gain control from being too aggressive and causing glitches (blind spots).
This resistor leaked enough current to the IF amps to keep signal during flutter with reflected signal conditions.
MICRON 35 MHz dual conversion receiver front end design thoughts (DC 11/2011) ∆
DAVID COLES HAS ENTERED THE ABOVE RECEIVER NOTES with details of his early Mike Dorfler Design Receiver. (thanks David!)
Hi, Came across your web postings re. Dorfler receiver.
I scratch built one of these around 1975, I used to buy Kraft servo kits from Custom RC in the Dartford area. The guy at C. rc sent me a photo copy of the American article. The picture of the pc board was not to scale. I took a photo and reduced the size using an enlarger, then made the board by marking the holes onto some thin pc board then hand painted/etched. I still have the photo copied article, some what faded now and my version of the receiver.
It's not been used for some years having moved on to 35Mhz and now 2.4Ghz.
hope this is of some interest to you.
The Micron design receiver above, bares a striking resemblance to the original DORFLER FET RECEIVER first published in American Modeller magazine. Mike Dorfler pioneered the use of the Field Effect Transistor as a mixer in radio control receivers.
David has sent us some info of his Dorfler receiver, assembled from the original article in American Modeller Magazine which is now over forty years old !
THE FOLLOWING IS AN EXTRACT FROM THE MAGAZINE ARTICLE :-
The Dorffler Micro F.E.T. I.C. Receiver
“If you are one of a growing number of mini-modelers, this very small two-channel receiver together with any of the new mini-servos and a 225mah battery pack should enable you to think even smaller.
It represents a substantial savings in size and weight over most current commercially available receivers. The two deck arrangement shown provides the greatest space savings from the design.
You can however, build it as a single decker as this is how the board is etched. The use of a F.E.T. (field effect transistor) makes for excellent sensitivity and helps to reduce the parts count in the front end. The absence of an additional antenna coil is offset somewhat by the low noise characteristics of this device. Integrated circuits are used in the decoder for maximum reliability and added parts savings. Altogether, the circuit offers one of the most modern designs available in the present R/C ‘state of the art’.
Because the receiver is quite compact, it is intended primarily for the experienced kit and scratch builder. A complete parts package will be available from Royal Electronics Inc. Denver Colorado.
Substitution of parts is not recommended, since the final reliability of the receiver would then be in question. Many items such as the case and plugs are left to the builder. The case shown in the photographs was constructed from 0.03” sheet plastic and glued together using liquid cement. The plugs are Deans but any should work. These just happen to be the lightest commercially available. Harness wiring and final system requirements are also left to the builder. All servos used have been KPS-12 mechanics with servo amplifiers built from Royal kits. The final weight of this two-channel system will be in the order of five to five and a half ounces using 225mah cells.”
Hey !...a blast from the past !
David Coles still has the above receiver, still working, but like us all, has now moved on to 35 Meg and now 4.2 GIG radio.
THE ORIGINAL MIKE DORFLER F.E.T RECEIVER CIRCUIT. ∆
this is a reverse-engineered circuit from an original receiver.
By David Caudrey.
WHILE ON THE MODEL STUFF and bringing in some history, Looks as if David Caudrey from the UK is on his second time around with a replica of a Kiel Kraft model he first made………(.well just a few years ago!) The photo shows the ‘KK Ladybird’ with present day motor (brushless electric) and radio gear installed. The original model was designed for Free-flight using an ED Bee 1cc diesel motor (Mark 1). (See Photo). ‘As a lad of about 14 years of age I built a KK Ladybird kit. I don’t think that the model can have been very well made because, with a lot of 1/8” ply to cut out with a razor blade it would not have been an easy build. With an ED Bee installed it flew and flew until the fuel rotted it. Fifty years later I decided to build another one and I was amazed to find that I couldn’t achieve anything like consistent trim. I tried a tail-plane of 50% greater area and even one with the symmetrical section replaced with a flat bottomed one but no two flights followed the same pattern. Fearing for my 1949 vintage Bee I replaced it with an Indian Mills 0.75 but eventually I lost interest. After languishing in the loft for nearly another 10 years, it occurred to me that it would be a nice subject for conversion to electric radio control. Recently completed, it has yet to fly as I am waiting for a calm day for a maiden flight.
Memories…Oh Memories….they do take a lot of beating, and to live them second time around….Magic.
Rattling the other day with ‘Technical Dave’, (David Caudrey) we got on to the subject of early British model engines. How these diesel and glow-plug motors stormed into, not only the UK market but so many were exported to many countries of the world. Let’s face it, this was British entrepreneurs showing not only how to design leading technology but also how to export products. OK…OK….these manufacturers were relatively small, probably consisting of perhaps around three key people in the business. These guys would do the original engine designs, design and set up special tooling and produce and assemble and even test the motors before sale.
However, These small manufacturing businesses also produced a market for other businesses !! To begin with they needed specialist die-casting people to supply the basic aluminium castings of the engines. They needed specialist manufacture of glow plugs (K.L.G comes to mind). They needed engineering machines, lathes, drilling, grinding machines etc to be bought in. Top quality supplies of aluminium rod, bronze, screws, ball bearings and plastic parts would also come from other suppliers. These people also needed (usually) to rent factory space to produce the engines. Printers and packaging people were also involved with instructions and packaging of a product capable of being transported around the World.
If you have managed to wade through the above, and are still with us! Then you can see how even a small manufacturing company not only produces three jobs, but also produces stability for dozens of other manufacturing jobs here in the UK. Sadly….the British manufacturing sub-soil has been eroded over the past few decades in favour of Banking and Finance. Not good for entrepreneurs.
Even more sad is the following list (David C’s research) of British Model Engine Manufactures that have become part of the UK Land-fill :-
Ace, Allbon, Allen Mercury, Amco, Allbon & Saunders, Atlas, BMP, Clan, Comet, Davies-Charlton,
Dragonfly, ED, Elfin, Embee, Eta(η), EPC, ERE, Foursome, Frog, Hallam, JB, Kalper, Kemp (K), Kingshire, Lionheart, ME,Miles, Milford, Nordec, Oliver, Owat, Redshift, Reeves, Rivers, Taplin, Weston, Yulon, ZA, Merco.
As you can see, we have not only lost these manufacturers forever and the orders they gave to other companies…..but also money coming into the UK from exports.
The picture you see above is our last remaining manufacturer of precision model engines….PAW. they survived the politics.
MEMORIES OF TIMES GONE BY
I did not build the Eaglet. It was given to me by a friend, Dennis Mursell, who is a member of the Basingstoke club. He was aware of my interest in scaled up versions of models which I built in my youth. I believe that Dennis built it from an RCM&E plan and he didn’t find it pleasant to fly. It came to me covered in his favorite ‘ natural linen’ Solartex with blue decoration. I converted it for free flight and fitted an AE 1.5cc engine in which form it flew beautifully with an impressive, if unrealistic, rate of climb. I gave it to another friend, Dave Warren, who was just getting into free flight. Dave re-covered it in orange and blue nylon and fitted a DC Spitfire as the AE was not that easy to start. Dave flew the Eaglet frequently until the nylon began to look rather tatty from fuel soakage. As he was moving to Shropshire and reducing his fleet of models, Dave asked me whether I would like to have it back. I decided that It would be nice to return it to radio control using a geared 480 and three cell LiPo battery; re-covering it black and yellow with my favorite Solite. It was necessary to use black on the fuselage to mask oil stained balsa.
I soon found why Dennis didn’t find it pleasant to fly. Like most free flight designs converted to radio control one expects a tendency to Dutch roll unless turns are initiated very gently. For the Eaglet this tendency is excessive and, unless the centre of balance is well forward of normal, it is virtually un-flyable. Balanced at about 15% of chord, it flies fast but it is twitchy and reluctant to climb, which greatly adds to the excitement.
D.I.Y ANODIZING OF SPINNERS AND CYLINDER BARRELS USING OLD BATTERY ACID!......well this one of the next projects to be covered by DC. David has a deep interest with model engine history and has achieved some amazing re-anodizing of collector engine parts. All done in the back garden shed with readily obtainable materials. Red and Blue anodizing has been achieved so far which can bring back some originality when renovating some of the old collector items. (see picture of the vintage ED Racer 2.5cc left which has had the makeover!). The anodizing process is not confined to vintage engines. New diesels and glow engines can also take on a special customized look with chosen aluminum parts anodized by the owner. It is interesting that our UK diesel manufacturer P.A.W withdrew engines with anodized parts in June 2007. (see picture right of the PAW 09 CT of 2006). So if you have a P.A.W motor that was purchased after June 2007 and want an older look, then keep reading and you will be able to do just that. See UK PAWs at www.paw.ac
AND IN THE BEGINNING: (1940s)…….THERE WERE SMALL SPARK IGNITION PETROL MODEL MOTORS, THEN THERE WERE SMALLER DIESEL MODEL MOTORS FOLLOWED BY EVEN SMALLER GLOW-PLUG MOTORS! Even though UK petrol prices are at an all time high, spark ignition petrol motors are still the least expensive to run. A typical petrol/oil mix would still work out less than £10 a gallon. Glow plug motor fuels are around £14 to £25 per gallon depending on additives. Diesel motors are the most expensive to run at around £50 per gallon.
Fuel consumption also comes into play, with petrol giving the best (minimum) fuel consumption. Diesel motors follow close behind petrol versions for fuel consumption. Glow motors consume the most fuel per revolution.
Considering the flying weight of the three motors….Petrol is the heaviest package as spark ignition units are necessary along with a battery. Diesels are the next heaviest motor as many of the internal parts are more robust to work with the higher working compression ratios. Glow motors have generally the lightest flying weight.
Both petrol and diesel motors are generally ported and timed to run slower with ‘grunt’ (more torque) to throw relatively larger props. Glow motors, have lighter internal moving parts and are often better dynamically balanced. These are often timed to run at higher revs with relatively smaller props. (more explosions per minute, making up their brake horse power formulae).
OK..WE ARE NOW INTO THE ANODIZING THING! (see D.I.Y. anodizing above)
ANODIZING AND DYING MODEL AIRCRAFT ENGINE PARTS DC Feb 2012
Becoming interested in building and flying the models which gave me so much pleasure as a youth, I purchased a number of small second hand Diesels in the 1990s. Running examples of the more popular types could be obtained fairly cheaply, particularly if they were not in pristine condition. The original manufacturers often used to increase the appeal of these little engines by anodizing some of the aluminum alloy parts such as cylinder heads, cylinder cooling jackets and spinner nuts and dyeing them bright colors. With use and age these colored parts become scratched or faded making them look very tatty. Initially the aesthetic appeal could be improved by removing the damaged decoration mechanically; using fine silicon carbide paper, old hacksaw blades etc. and spinning the parts with an electric drill. The appearance and durability of these cleaned up parts could also be improved by neutral anodizing which gives them a pearly dove grey finish and I used this method to good effect on a couple of really tatty DC Spitfires. Success with this process made me wonder whether the parts could be re-colored using dyes from the Dylon range sold in Woolworths and other outlets. I soon found that my pearly finished parts would not take dye because the aluminum oxide coating wasn’t porous. However, with some test pieces, I found that the anodized surface would take dye if the anodizing process, and thus the thickness of oxide, was not sufficient to give the pearly appearance.
Anodizing, as the name indicates, is the process of depositing a thin protective oxide layer on aluminum or aluminum alloy by making the part the anode of an electrolysis cell using dilute sulphuric acid as the electrolyte. I am the first to admit that the method I have used is crude and without precision but, with a few caveats, it can be used to replicate the original colors. Red I found to be quite easy to do but greater care is needed for blue. Green has not been really successful because the Dylon range doesn’t appear to include a bright green dye. (There is such a dye in the cold water range but these do not seem to work on aluminum oxide). Yellow-gold I have yet to try but black (actually navy) did not prove to be difficult to do.
With the advent of the ‘Nanny Society’ it has become difficult for individuals to purchase chemicals which were freely available when I was young. However two of the three involved – washing soda and caustic soda – are freely available. For the all-essential sulphuric acid I have drained old car batteries (best to charge them before draining to get the purest condition) but even that is becoming more difficult with modern developments.
These chemicals are corrosive but I will not insult potential users by lecturing them on safety, other than to say eye protection is a must at the very least. Also the anodizing tank will give off acid fumes so do not stay close to it whilst it is operating.
Referring to the sequence diagram: - For the degreasing tank, the washing soda and caustic soda crystals are mixed in the ratio 3:1 respectively and sufficient demin. water is added to dissolve them. (watch out the solution can get pretty hot).
In the anodizing tank it is a bit of a race between the corrosive effect of the acid and the protection afforded by the oxide. Battery acid is a bit too corrosive for 40 tpi. threads etc. so I dilute it 1 part acid to 2 parts water. In fact, as the threads of a cylinder jacket are not visible, it is better not to remove the original anodizing from them. With this dilution the cell resistance is still low enough to get reasonable current levels with the circuit depicted in the diagram.
The depth of anodizing depends upon the product of current and time. The normal deposition depth ranges from about one tenth of a thou to three tenths of a thou (in ‘Christian units’) from ‘soft to hard’. Dye is taken up readily in the first half of the range but does not seem to penetrate hard anodising. References on the subject mention current densities of around 10 Amps per square foot or greater but as it is not always easy to determine the surface area of an object to be anodized I use the following rule of thumb products for a dyeable deposition:-
A DC Spitfire/Sabre jacket - Half an Ampère hour to one Ampère hour.
A DC spinner nut - A quarter of an Ampère hour to half an Ampère hour.
It is probably better to err on the low side initially because the item can always be returned to the tank if the colour is very transparent due to insufficient depth of oxide as appeared to be the case for the last of the DC engines manufactured.
Whatever the actual value of the current used, the electrolyte must not get hot, (> 50oC) otherwise the anodizing will seal and not take dye.
Once the electrolysis is complete the item is washed in demin. water and then transferred to the dye tank in which the dye solution has been prepared according to the manufacturer’s instructions. Being a hot water dye the solution should be heated to just above blood heat.
The item should be stirred around in the solution to eliminate trapped air and the strength of color attained is to some extent determined by the length of time that the item is in the solution.
When the color is as required the item is rinsed in cold water and then plunged into boiling water, or held in the steam from a kettle, to seal the surface and complete the process.
SUCCESSES AND FAILURES
The photographs show the results of red anodizing of Jackets and spinner nuts of a DC Sabre and of an ED Racer belonging to a friend (he supplied me with a copious amount of acid recovered from batteries dumped along the verges of a stretch of the A11 presumably by car rescue firms – the mind boggles!). At this time I omitted a washing stage between anodizing and dyeing because it didn’t seem to matter that a little acid was carried over to the dye.
When I tried to do a Spitfire Jacket blue things went very wrong. It came out of the dye a plum color, nothing like the deep blue I was expecting. After some thought I realized that the blue dye was acting like litmus and I was carrying over acid from the anodizing tank. I proved this by adding caustic soda to the dye and turning it back to blue but, as the dye was now corrupted, I neutral anodized the jacket for the Spitfire shown in the photograph with the plum colored failure. However I had learnt the need for washing between the processes if nothing else.
My final experiment was with navy dye. Back in the 1990s I was given a marine ED Super Fury which I wanted to convert to aircraft form. A friend kindly turned up a jacket and prop driver to his own design. The engine was installed in a 1.5 x KK Pirate for a number of years and it gave me some amusement because the ‘experts’ were always querying what it was. The engine eventually came to grief through the Pirate flying head on to a brick bunker, cracking the cylinder. Being left with the jacket I decided to try to anodize it black. However my local chemist, who keeps only a limited range of Dylon dies, only had navy so I tried that. This was very successful as the photograph shows.
It is possible that the Fury might run again as with a bit of fettling I think that I can adapt a DC Sabre cylinder assembly to fit. If nothing else it will be an interesting experiment.
For an update on ‘home anodizing’ see David’s latest notes on Page 25 (you can go direct by clicking here).
OK..A CHANGE OF SUBJECT WITH THIS NEXT READER INPUT. AN INTERESTING CONVERSION OF A VINTAGE JR RADIO TO 2.4 GIG.
BY PETER GASCOINE.
Thanks for the email.
I had been using a plug-in Frsky module in my original JR3810 Tx for some time until the module pins became loose causing a radio failure. The 3810 was quite old (2nd hand) so I hard wired in the Frsky "hack" module, and since then had no further problems. This also had the benefit of replacing the 35MHz antenna with the 2.4 item.
I have also built a single channel transmitter using Phil G's encoder module and attach a couple of photos of this complete with Sharkface. This operates the rudder servo as a bang-bang (as per Elmic Conquest escapement) control which was how I flew my original Sharkface in the 60s - photo attached. Both Frsky units have excellent range and bind on switch-on faster than my Spektrum DX7 ! .
The above brings many memories of one of the first aerobatic single channel models ! with the Cox .049 it must shift like stink ! The conversion uses a ‘proper’ solid on/off switch too….and what looks like a professional Micro Switch that can be heard a few yards away (old money!). More of Phil G’s stuff can be found by clicking here.
Thanks for reading !